Field of the Invention
The present invention relates to an image processing apparatus, a method of controlling the same, and a storage medium, and more particularly to a method of deleting encrypted data and unencrypted data stored in the image processing apparatus.
Description of the Related Art
Information processing apparatuses capable of accumulating information using a storage device, such as a hard disk drive (HDD), include one configured to temporarily store received information (hereinafter also referred to as “data”) in the HDD, and delete the data from the HDD after completion of processing using the data. In this information processing apparatus, the HDD stores data and position information indicative of locations of the data on the HDD (hereinafter referred to as “the FAT (File Allocation Table)”). When data is deleted from the HDD, generally, only the FAT is deleted from the viewpoint of high-speed data deletion processing. The data remaining on the HDD is overwritten with other data sooner or later.
However, if the data remains on the HDD when the above-mentioned information processing apparatus is discarded, there is a fear that the data is stolen by removing the HDD from the information processing apparatus, and connecting the HDD to e.g. a computer (PC) for analyzing the data.
In recent years, as the awareness of information security increases, an overwrite deletion function for deleting not only a FAT but also data remaining on the HDD has come to be widely known. In an information processing apparatus having this overwrite deletion function, data is prevented from remaining by writing 0's, random numbers, or fixed values, over the data no longer needed, once or a plurality of times (see e.g. Japanese Patent No. 3715711).
However, when discarding the information processing apparatus, it is necessary to write overwriting data in all storage areas on the HDD, which brings about a problem that it takes a long time to perform overwrite processing in proportion to the capacity of the HDD. Further, as a method of protecting data on the HDD, data protection by encryption is widely used. In the publication of Japanese Patent No. 4606808, to solve the above-mentioned problem of the processing time, there has been proposed a method of reducing the overwrite processing time by performing, as a means for deleting encrypted data, overwrite deletion of a minimum amount of data required to be deleted so as to make it impossible to decrypt the encrypted data.
However, in the technique described in Japanese Patent No. 4606808, it is difficult to selectively and efficiently delete data on the storage device within a short time period in an environment in which an encrypted data area and an unencrypted data area are mixed on the storage device, or in an environment in which encryption of data depends on settings therefor.